You can't prevent double spending without being able to track where individual coins go. So we can know that X BTC went from wallet A to wallet B. Bitcoin is an

You can't prevent double spending without being able to track where individual coins go. So we can know that X BTC went from wallet A to wallet B. Bitcoin is anonymous in the sense of linking owners to wallets. Even if someone asks to send Y bitcoins to wallet C as payment for something, you can't know from the wallet address where the wallet is stored or even if it isn't the wallet of a third party to whom that someone owes bitcoins.